Concentrating solar power receivers have been made in a number of different configurations. Pressurized air (high pressure) and open air (low pressure) solar power receivers have both been tested successfully in research facilities and pre-commercial demonstration plants have been built. Prior receivers that can generate hot pressurized air include tubular receivers and closed volumetric receivers.
Tubular receivers are termed indirectly-irradiated receivers and generally consist of multiple high temperature resistant metal alloy boiler tubes through which is passed a pressurized working fluid such as compressed air, water/steam, carbon dioxide or any other suitable working fluid.
On the other hand, open and closed volumetric receivers are regarded as directly-irradiated receivers. Closed volumetric receivers typically make use of a pressurized quartz window through which solar irradiation passes and strikes a porous absorber medium inside a pressurized chamber. Pressurized gas moves through the absorber medium and thus gains thermal energy while cooling down the absorber medium.
The heated pressurized gas, typically air, may be used for a variety of different purposes and one that is of particular interest to the applicant is to energize a gas turbine that is used to drive a suitable machine such as an electrical generator.
A number of other heat collection arrangements have been proposed and the present invention presents an alternative that it is envisaged may have particularly effective results.
One of these is disclosed in European patent application publication number EP2520872. In the arrangement described multiple pyramidal elements are carried by a common chamber wall and heat transfer fluid to be heated is introduced to the apex of each of the pyramidal elements and become heated as it flows between the outer wall of the pyramidal element that become heated by solar energy and an inner pyramid wall spaced inwardly of the outer wall. The concept is to attempt to trap solar energy between the converging outer walls of adjacent pyramids.
It is to be noted that for the purposes of this specification the term “tube” is intended to mean an elongate hollow cylinder of generally constant cross-sectional shape along its length. Typically, the length of the tube will be at least twice and generally at least five times the cross-sectional size, and most commonly from 5 to 20 times the cross-sectional size, or more.